Experiments are proposed to study pulmonary CO2-sensitivity in mammals. The objectives of this proposal are to (1) define the mechanisms responsible for the homeostasis of arterial PCO2 during CO2-loading and (2) to identify anc characterize pulmonary receptor systems which are sensitive to CO2. Reflex and electrophysiological techniques are proposed. Reflex studies are planned to determine the role of pulmonary chemosensitivity in the regulation of arterial PCO2 and to define the interaction between pulmonary chemosensitivity and the peripheral arterial chemoreceptors in the regulation and arterial PCO2. Further studies are planned to investigate the nature of the pulmonary chemosensitivity. Electrophysiological studies involve the use of microelectrodes to record single unit pulmonary afferent activity from the nodose ganglion. The static Co2-sensitivity of pulmonary afferent neurons will be studied in detail. BIBLIOGRAPHIC REFERENCES: Osborne, J.L., Burger, R.E., and Stoll P.J. Dynamic responses of CO2-sensitive avian intrapulmonary chemoreceptors. Amer. J. Physiol. (Regulatory, Integrative and Comparative Physiology Section), 1977 (In press). Osborne, J.L., and Mitchell, G.S. Intrapulmonary and systemic chemoreceptor interaction in the control of avian respiration. Respir. Physiol., 1977 (In press).